The goal of this proposal is to achieve an increased understanding of the etiology and treatment of idiopathic sudden hearin loss by the systematic collection and evaluation of clinical data. Our objectives include the serologic evaluation of acute and convalescent sera for the purposes of identifying the principle virus(es) responsible for SHL, and the determination of the relationship between virally induced SHL, to other pathological, demographic, or environmental factors. In addition, we will continue a collaborative clinical study at MEEI, WVU< and K-P Oakland assessing the relationship of ISHL to hereditary, epidemiological, and occupational factors by means of statistical analysis of data obtained from ISHL patients. Also, we will assess the relationship between microvascular disease, diabetes mellitus, and sudden hearing loss. Finally we will determine the correlation between electronystagmography, Hallpike Caloric testing, vestibular or cochlear injury, and the etiology and the degree of loss and recovery from SHL. The significance of these studies is to increase our understanding of the etiology, classification, and treatment of sudden hearing loss, as well as to lend further insight into the pathophysiologic mechanisms of sensorineural hearing loss in general.